Objects aren't visible when I render the image
LAYERS




Do the following for every object from largest object to the smallest.  In the object panel / Relations click on layer (1) so it is dark as in the image above, the upper left layer rectangle of 20 possible.  Then click render.
These layers are coordinated with these Render Layer Settings


 

When a new simple file is created objects are on layer 1 and the render layer settings are showing at least layer 1.  Blender gives the user the flexibility to hide or show these layers at different times and phases.  It can be used as a feature or to create confusion.

If you want to know more you can now search at this website and blender.org and video site for information about [layers].  Quick Summary.  Every file can have multiple render layers.  Every render layer can select some of the twenty layers.  Every object can be on some render layers.  All 3 concepts must be coordinated with other hidden delights for an object to appear in the render.